This invention relates to a lens holder driving device and, in particular, to fixed structure of a driving coil for a lens holder.
Mobile terminals such as camera-equipped cellular mobile phones often mount compact cameras therein. The compact camera is provided with an autofocus lens holder driving device. Previously, various autofocus lens holder driving devices have been proposed. As a driving source (a driving method) for use in such as a lens holder driving device, a VCM method using a voice coil motor (VCM) is known. The lens holder driving device of the VCM method comprises, as the driving source (a driving portion), a driving coil (a coil) and a magnetic circuit which is composed of a yoke and a permanent magnet. The lens holder driving device is also referred to as an actuator. The driving sources (driving portions) of the VCM method are broadly divided into driving portions of “moving coil method” and driving portions of “moving magnet method.”
On the other hand, a lens holder driving device of the type described comprises a lens holder (a lens supporting body) for holding a lens assembly (a lens). In the lens holder driving device comprising the driving portion of “moving coil method”, the above-mentioned driving coil (coil) is fixed to the lens holder (the lens support body). Previously, various fixed structures have been adopted.
By way of illustration, in a lens holder driving device disclosed in Japanese Unexamined Patent Application Publication No. 2008-310237 (JP-A-2008-310237) (which will also be called Patent Document 1), a coil is fixed to an outer side of a lens supporting body. The lens supporting body comprises a plurality of coil fixed portions each projecting in a radial direction outwards and the coil has a bottom portion which is fixed to the coil fixed portions.
In addition, in a lens holder driving device disclosed in Japanese Unexamined Patent Application Publication No. 2009-265210 (JP-A-2009-265210) (which will also be called Patent Document 2), a coil is bonded and fixed to a coil fixed portion which is integrally provided to a lens supporting body. The lens fixed portion projects from the lens support body in a radial direction outwards. Accordingly, the coil has a bottom portion which is bonded and fixed to the lens fixed portion.
In a lens holder driving device disclosed in Japanese Unexamined Patent Application Publication No. 2006-208427 (JP-A-2006-208427) (which will also be called Patent Document 3), a flange portion mounted in a rim of a lens support body is provided with a coil mounting portion and a coil has a bottom portion which is bonded and fixed to the coil mounting portion. In Patent Document 3, the coil mounting portion has a surface on which an infinite number of bumps and dips are formed in order to expand an adhesive area of adhesives and thereby enhancing adhesive strength for the coil. In this event, the coil is bonded and fixed to the coil mounting portion by filling the adhesives between the bottom portion of the coil and the bumps and dips in the coil mounting portion.
In a lens holder driving device disclosed in Japanese Unexamined Patent Application Publication No. 2007-316395 (JP-A-2007-316395) (which will also be called Patent Document 4), a coil is fixed to an outer side portion of a lens supporting body. Patent Document 4 illustrates, in FIG. 2 thereof, that the outer side portion of the lens supporting body has grooves which are bored in parallel with an optical direction. It seems that the grooves are filling grooves for pouring adhesives in order to fix the coil to the outer side portion of the lens supporting body on bonding.
In the above-mentioned lens holder driving devices disclosed in Patent Documents 1-4, the bottom portion of the coil is bonded and fixed to the coil fixed portion (the coil mounting portion) of the lens supporting body.
In mobile terminals mounting the compact cameras provided with the autofocus lens holder driving devices having such fixed structures, there is a possibility of peeling the driving coil from the lens holder by moving (shifting) the driving coil for the lens holder in the optical direction caused by an impact on dropping the mobile terminals or the like.
For example, in Patent Document 3, it is difficult to inhibit (prevent) the coil from peeling from the lens supporting body against impact force of the coil for the lens supporting body in the optical direction because the coil is bonded and fixed to the coil mounting portion by filling the adhesives between the bottom portion of the coil and the bumps and dips in the coil mounting portion.
In addition, in Patent Document 4, the filling grooves bored to the outer side portion of the lens supporting body in parallel with the optical direction are for pouring the adhesives on boding and are not for enhancing the adhesive strength of the coil for the lens supporting body as the above-mentioned Patent Document 3.